1. Field of the Invention
The invention relates generally to a machine tool system for processing symmetrical and asymmetrical work pieces and, more particularly, to an apparatus of the kind including magnetically controllable loading or positioning devices.
2. The State of the Art
Work pieces may be mechanically processed on machine tools such as lathes, milling machines or boring mills. Also, manufacturing systems are known utilizing CNC (computer numerical control) machine tools.
The incorporation of machine tools or even machine systems in assembly lines has become common practice for reducing idle times in mechanical processes to increase productivity and broaden manufacturing possibilities.
To meet these requirements, solutions have been proposed in respect of such operations as loading and unloading of work pieces on tool clamping plates and the like, the aligning of work pieces relative to tools, the adjustability of work pieces in process relative to a tool, as well as machine tool drives.
Thus, German laid-open patent specification DE-OS 2,102,234 relates to a drive for moving work piece supports to predetermined positions of a transport path within an assembly line.
This is accomplished by utilizing a plurality of primary and secondary components of well-known linear motors which cooperate reciprocally or by impulse excitations. The primary components are distributed in the transport path individually or in groups, and the secondary components are arranged on the tool support. Those components which are arranged in groups are disposed in parallel or angularly. Certain groups of primary components are alternatingly and consecutively connectible to three-phase-current and direct current sources by the tool support. Each of the secondary components consists of a plate of high magnetic conductivity facing the primary component and is covered by a plate of high electric conductivity, each one of which is longer than each of those primary components which are disposed in the same direction as they are. Two parallel strips of high magnetic conductivity are transversely embedded in the plate of high electric conductivity, each strip being wider than the width of the grooves of the primary components and the spacing of which, measured from their centers, corresponds to two dissimilar poles of the primary components.
In this apparatus, an air cushion is generated between the tool support and the transport path, and a known linear motor is used as a drive.
Setting up or lifting by means of a magnetic loading plate is also known, and European patent specification 0,357,904 A1 describes a magnetic loading plate capable of securely supporting not only work pieces made of different materials, even weakly or non-magnetic ones. Yet its surface structured such that even though support of the work piece is not lacking at any point, an assured and good vacuum transmission and unimpeded air flow is nevertheless possible.
Two embodiments are described. In one embodiment, slots and bores in the magnetic pole sections are formed between the pole conductors made of non-ferromagnetic material, and they are filled with fine-pored sintered metal. In the other embodiment, the slots are provided in the pole conductors and they are filled with fine-pored sintered metal as well, which in this case, however, is non-ferromagnetic.
Whilst with this proposed combined vacuum-magnetic loading plate retention by magnetic forces is possible, other possibilities such as, for instance, positioning or moving work pieces provided on the loading plate is not possible in accordance with this solution.
European patent specification 0,637,482 A1 discloses a method of positioning a tool support in a processing machine as well as an associate tool support, in which the work piece support is moved to, and is arrested in, a position corresponding to an approximate desired position, the actual position being thereafter determined by at least two reference marks provided on the work piece support. The work pieces clamped in the work piece support are then measured at a measuring location especially equipped for that purpose. The measurement data thus derived are transferred to the processing machine. The true position of the work pieces on the processing machine can then be calculated on the basis of the position of the two reference marks. Moreover, a tool support is proposed provided with at least two horizontally spaced reference marks for registering its position relative to the X and Y directions as well as its angular position around the Z axis.
Whilst this method does relate to positioning of a tool support in an processing machine, the realization of the method is very complex, the clamping elements provided serve to clamp and arrest the work piece support, whereby actual clamping is to take place mechanically, preferably by spring force, and release is to take place pneumatically.
The described known solutions relate exclusively to individual process steps or process sequences of machine tools. Combined or several continuously running operations are not possible with the said solutions.